Toxicidade letal e subletal do óleo de nim aos ácaros Mononychellus tanajoa e Proprioseiopsis neotropicus (Acari: Tetranychidae, Phytoseiidae)

Abstract

The lethal concentration (LC) is usually used to evaluate the toxicity of pesticides to arthropods, however it is considered an incomplete measure as it estimates only the mortality as a parameter of toxicity. Arthropods that survive pesticide spraying suffer with physiological and behavioural sublethal effects. Growth rate and lethal concentration studies have been recommended to evaluate the toxicity of pesticides to arthropods because they consider mortality and sublethal alterations on fecundity. Similarly, studies of biological parameters of arthropods may reflect sublethal effects of pesticides. Here, we used the LC and the growth rate in order to evaluate the lethal and sublethal toxicity of the oil of neem to the predatory mite Proprioseiopsis neotropicus and the cassava green mite Mononychellus tanajoa. The LCs50 of the oil of neem to P. neotropicus and M. tanajoa were 0.00748 ml/cm2 and 0.00328 ml/cm2 , respectively, indicating a higher tolerance of the predatory mite to the pesticide. The instantaneous rate of increase of P. neotropicus decreased with increasing concentrations of the oil of neem, although population increase was observed even after exposure to the LC50 of the oil of neem. Overall, the biology of P. neotropicus was not affected by the LC25 of the neem oil. The duration of immature phases of M. tanajoa were faster when exposed to the LC50 of the oil of neem. In conclusion, the oil of neem has lethal and sublethal toxicity to the mites P. neotropicus and M. tanajoa, however by having a higher toxicity on the cassava green mite in comparison to the predatory mite it may be an alternative to the management of this pest